A fusible switch is usually mounted in an enclosure and incorporates an insulating base to carry an incoming line terminal for each phase. The circuit for each phase is completed through a pivotal knife blade which engages a corresponding contact stab and is electrically connected with a fuse clip having a fuse seated therein. In U.S. Pat. No. 4,302,643, commonly assigned to the Square D Company, a fusible switch is shown utilizing the above-mentioned construction and which is hereby incorporated by reference in its entirety.
Fusible switches are used in switchboards to distribute power for commercial and industrial applications. The need arises to distribute more power through enclosures which are the same size or smaller. This requires increasing the electrical rating of the switch to carry a higher voltage and current density while decreasing the size of the enclosure housing the electrical parts.
Among the problems caused by decreasing the space requirements of a switch is the additional hardware necessary for mounting different types and classes of fuses in a fusible switch. Usually, only one class of fuse will fit in a fuse holder. Furthermore, mounting screws are used to attach and retain fuse clips and other terminals to switch base interiors. The need arises to assemble the fuse switches in increasingly smaller enclosures providing little room for maneuvering. This requires electrical components which can be assembled without complicated tools, or preferably, without any tools.
Other problems caused by assembling the fusible switch interiors is the quantity of parts that must be tracked, inventoried, and supplied in the field to properly complete the assembly. A reduced part count and less manual labor during assembly would decrease installation time and cost.
Furthermore, the parts for the switch interior must be economical to manufacture. A switch which assembles easier and faster at a comparable cost allows more wide-spread application.